Transparent, highly heat-resistant polyimide precursor and photosensitive polyimide composition thereof

ABSTRACT

The present invention relates to an aqueous alkali-developable photosensitive polyimide precursor resin composition that is appropriate for highly heat-resistant transparent protection layers and insulation layers for liquid crystal display devices. In more detail, the present invention relates to a negative-type photosensitive transparent polyimide precursor resin composition manufactured in two steps. The first step is the manufacture of a transparent linear polyamic acid (A) from (a-1) one or more kinds of tetracarboxylic acid dianhydrides selected from alicyclic tetracarboxylic acid dianhydrides having 3 to 30 carbon atoms; and (a-2) one or more kinds of diamines selected from aliphatic, alicyclic, or non-conjugated aromatic diamines, having 3 to 30 carbon atoms, having one or more ethylenically unsaturated bonds at side chains as essential components; and the second step is the manufacture of reactive transparent polyimide precursors shown in the following Chemical Formula 1 according to the esterification reaction of the above polyamic acid (A) with ethylenically unsaturated compound (B) containing an epoxy group in the same molecule as the main component. The photosensitive transparent polyimide precursor resin compositions according to the present invention have a superior photosensitivity, and thus, may be used for transparent protection layers and insulation layers of liquid crystal display devices having superior heat resistance, chemical resistance, mechanical strength, and electricity insulation.

This application claims priority to PCT/K2004/000640, filed on Mar. 24,2004, and Korean Application Nos. 10-2003-0018127 filed Mar. 24, 2003,in Korea, all of which are hereby incorporated by reference in theirentirety.

TECHNICAL FIELD

The present invention relates to an aqueous alkali developablephotosensitive polyimide precursor resin composition that is appropriatefor highly heat-resistant transparent protection layers and insulationlayers for liquid crystal display devices. In more detail, the presentinvention relates to a negative-type photosensitive transparentpolyimide precursor resin composition manufactured in two steps. Thefirst step is the manufacture of a transparent linear polyamic acid (A)from (a-1) one or more kinds of tetracarboxylic acid dianhydridesselected from alicyclic tetracarboxylic acid dianhydrides having 3 to 30carbon atoms; and (a-2) one or more kinds of diamines selected fromaliphatic, alicyclic, or non-conjugated aromatic diamines, having 3 to30 carbon atoms, having one or more ethylenically unsaturated bonds atside chains as essential components; The second step is the manufactureof reactive transparent polyimide precursors shown in the followingChemical Formula 1 according to the esterification reaction of the abovepolyamic acid (A) with ethylenically unsaturated compound (B) containingan epoxy group in the same molecule as the main component.

BACKGROUND ART

Generally, polyimide resins are manufactured through condensationpolymerization of aromatic tetracarboxylic acid or its derivatives andaromatic diamine or aromatic diisocyanate, and thus manufacturedpolyimide resins have superior heat resistance, chemical resistance,mechanical and electrical properties. Photosensitive aromatic polyimideshaving such superior properties are widely used for electronic materialssuch as semiconductor encapsulant, etc.

However, aromatic polyimides are not appropriate for transparentprotection layers or insulation layers for liquid crystal displaydevices in that they have low transmittance in the visible region, arecolored in yellow or brown, and have a relatively high dielectricconstant. Epoxy resins or acrylic resin compositions have been widelyused as transparent protection layers or insulation layers for liquidcrystal display devices. But their inherent heat resistancecharacteristics practically limits subsequent processing condition tobelow 230° C. When they are processed at temperatures of 250° C. orhigher, severe decoloration and film contraction may occur.

Accordingly, polyimide materials have been taken into consideration inorder to meet heat resistance and transparency simultaneously, and somemethods of manufacture of polyimides by using alicyclic acid anhydrideshave been reported as studies for obtaining transparent polyimidemembrane or film (Macromolecules, 1994. 27, 1117 and 1993, 26, 4961,Japanese Patent Laid-Open No. PYUNGSUNG9-95533, Japanese PatentLaid-Open No. 2001-330721).

However, in order to use such non-photosensitive transparent polyimideresins as protection layers or insulation layers for liquid crystaldisplay devices, the process of minute pattern formation by lithographyprocess should be added after polyimide film formation on substratescomposed of glasses, etc.

While the use of photosensitive transparent polyimide resin compositionsis advantageous in view of cost reduction since the above-describedprocess can be simplified, the photosensitive transparent polyimideresin composition using trans-1,4-diaminocyclohexane reported inJapanese Patent Laid-Open No. 2002-161136 is practically inapplicabledue to too slow photosensitivity.

The inventors of the present invention has reported photosensitivetransparent polyimide resin compositions in Korean Patent ApplicationNo. 10-2002-074070 leaving the development margin and photosensitivityto be improved further.

DISCLOSURE OF INVENTION

In order to resolve the above-described problems, an object of thepresent invention is to provide a negative-type photosensitivetransparent polyimide precursor having enough photosensitivity, and toprovide compositions that may be used for transparent protection layersand insulation layers for liquid crystal display devices having superiorheat resistance, chemical resistance, mechanical strength, electricalinsulation, and a method of preparing the same.

The foregoing and other objects, aspects, and advantages will be betterunderstood from the following detailed description of preferredembodiments of the invention:

In order to achieve the above objects, the present invention providesreactive transparent polyimide precursors having the following ChemicalFormula 1:

where X is a tetra-valent organic group induced from alicyclictetracarboxylic acid dianhydrides having 3 to 30 carbon atoms; Y is adi-valent organic group induced from aliphatic, alicyclic, ornon-conjugated aromatic diamines having 3 to 30 carbon atoms; R₁ and R₂are hydrogen atoms or organic groups having 1 to 20 carbon atomsincluding one or more ethylenically unsaturated bonds, and R₁ and R₂cannot be hydrogen atoms at the same time.

The acid value of the above reactive transparent polyimide precursorsmay be in the range of 30 to 200 mg KOH/g, and the molecular weight ofthe above reactive transparent polyimide precursors may be in the rangeof 2,000 to 200,000.

Also the present invention provides a method of preparing reactivetransparent polyimide precursors of the above Chemical Formula 1,comprising the steps of: manufacturing a transparent linear polyamicacid (A) having (a-1) one or more kinds of tetracarboxylic aciddianhydrides selected from alicyclic tetracarboxylic acid dianhydrideshaving 3 to 30 carbon atoms, and (a-2) one or more kinds of diaminesselected from aliphatic, alicyclic, or non-conjugated aromatic diamineshaving 3 to 30 carbon atoms including one or more ethylenicallyunsaturated bonds at side chains; and esterifing the transparent linearpolyamic acid (A) with an ethylenically unsaturated compound (B)containing an epoxy group in the same molecule.

The above-described tetracarboxylic acid dianhydrides may be one or morekinds of anhydrides selected from 1,2,3,4-cyclobutanetetracarboxylicacid dianhydride (CBDA), 1,2,3,4-cyclopentanetetracarboxylic aciddianhydride (CPDA), bicyclooctene-2,3,5,6-tetracarboxylic aciddianhydride (BODA),5-(2,5-dioxotetrahydrofuran-3-yl)-3-methylcyclohexene-1,2-dicarboxylicacid anhydride (DOCDA),4-(2,5-dioxotetrahydrofuran-3-yl)-tetralin-1,2-dicarboxylic acidanhydride (DOTDA); and the above diamine may be one or more kinds ofdiamines selected from those having the general chemical formula shownin the following Chemical Formulas 7 to 9:

where Z is one of ester, amide, imide, ether, and carbonyl group; R₃,R₄, and R₅ are hydrogen atoms or alkyl or allyl groups having 1 to 20carbon atoms; and n is an integer between 1 to 20.

The diamines in the above may be one or more kinds of compounds selectedfrom the group consisting of 2-(methacryloyloxy)ethyl3,5-diaminobenzoate, 3,5-diaminophenyl cinnamate, and coumaronyl3,5-diaminobenzoate.

The above ethylenically unsaturated compound (B) containing an epoxygroup in the same molecule may be one or more kinds of compoundsselected from the group consisting of allyl glycidyl ether, glycidylacrylate, glycidyl methacrylate, 3,4-epoxycyclohexylmethyl acrylate,3,4-epoxycyclohexylmethyl methacrylate, glycidyl5-norbornene-2-carboxylate (a mixture of endo and exo), glycidyl5-norbornene-2-methyl-2-carboxylate (a mixture of endo and exo),1,2-epoxy-5-hexene, and 1,2-epoxy-9-decene.

The present invention also can be characterized by providingphotosensitive polyimide precursor resin compositions using theabove-mentioned transparent polyimide precursors and one or more kindsof photo-initiators as essential components, and adding one or morekinds of compounds selected from the group consisting ofphotosensitizers, multi-functional monomers, and common coatingadditives.

The portion of the above-described reactive transparent polyimideprecursors may be 10 to 99 weight %, and that of the photo-initiatorsmay be 0.1 to 90 weight %, based on the amount of total solids.

Thickness of polyimide films coated and postbaked may be 0.5 to 100 μm;thermal decomposition temperature of polyimide films in the range of 300to 500° C.; transmittance between 400 to 700 nm of polyimide films ofthe above compositions 90% or higher; and dielectric constant measuredat 1 kHz of the above compositions in the range of 2.5 to 4.0.

The present invention can also provides transparent protection layer orinsulation layer, which is prepared by using the photosensitivepolyimide precursor resin compositions obtained in the above.

Further, the present invention can provide a liquid crystal displaydevice which is manufactured by applying the photosensitive polyimideprecursor resin compositions obtained in the above to its transparentprotection layer or insulation layer.

Still further, the present invention can provide a liquid crystaldisplay device which is prepared by applying the photosensitivepolyimide precursor compositions to the organic insulation materials forliquid crystal display devices.

Hereinafter, the present invention is described in more detail asfollows:

(a-1) is one or more kinds of tetracarboxylic acid dianhydrides selectedfrom alicyclic tetracarboxylic acid dianhydrides having 3 to 30 carbonatoms, of which concrete examples include, but are not limited to,1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA shown inChemical Formula 2), 1,2,3,4-cyclopentanetetracarboxylic aciddianhydride (CPDA shown in Chemical Formula 3),bicyclooct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride (BODA shown inChemical Formula 4),5-(2,5-dioxotetrahydrofuran-3-yl)-3-methylcyclohexene-1,2-dicarboxylicacid anhydride (DOCDA shown in Chemical Formula 5),4-(2,5-dioxotetrahydrofuran-3-yl)-tetralin-1,2-dicarboxylic acidanhydride (DOTDA shown in Chemical Formula 6), etc.

Also, if it is necessary, aromatic tetracarboxylic acid dianhydridesselected from the group consisting of pyromellitic acid dianhydride,benzophenone tetracarboxlic acid dianhydride, oxydiphthalic aciddianhydride, hexafluoroisopropylidenediphthalic acid dianhydride, etc.may be used as well as long as they do not deteriorate the transparencyof the polyimides.

(a-2) is one or more kinds of diamines selected from aliphatic,alicyclic, or non-conjugated aromatic diamines having 3 to 30 carbonatoms including one or more ethylenically unsaturated bonds at sidechains as essential components, of which concrete examples include2-(methacryloyloxy)ethyl 3,5-diaminobenzoate (Chemical Formula 7,R₃=CH₃, R₄=H, Z=COO, n=2), 3,5-diaminophenyl cinnamate (Chemical Formula8, R5=H, Z=OCO), coumaronyl 3,5-diaminobenzoate (Chemical Formula 9,Z=COO), etc. (where Z is one of ester, amide, imide, ether, carbonylgroup, etc.; R₃, R₄, and R₅ are hydrogen atoms or alkyl or allyl groupshaving 1 to 20 carbon atoms; and n is an integer between 1 to 20). Also,if necessary, diamines not including ethylenically unsaturated bonds inthe same molecule may be used as well as long as they do not deterioratethe transparency and chemical resistance of the polyimides thus formed.Their concrete examples include, but are not limited to, one or morekinds of compounds selected from the group consisting of1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane,para-phenylenediamine (p-PDA), meta-phenylenediamine (m-PDA),4,4-oxydianiline (ODA), 4,4-methylenedianiline (MDA),2,2-bis(aminophenyl)hexafluoropropane (HFDA),meta-bis(aminophenoxydiphenyl)sulfone (m-BAPS),para-bis(aminophenoxydiphenyl)sulfone (p-BAPS),1,4-bis(aminophenoxy)benzene (TPE-Q), 1,3-bis(aminophenoxy)benzene(TPE-R), 2,2-bis(aminophenoxyphenyl)propane (BAPP),2,2-bis(aminophenoxyphenyl)hexafluoropropane (HFBAPP), 5-diaminobenzoicacid, 2,4-diaminobenzenesulfonic acid, 2,5-diaminobenzenesulfonic acid,bis(aminopropyl)tetramethyldisiloxane, etc.

Hereinafter, a method of preparing a reactive transparent polyimideprecursor according to the present invention is described as follows:

<Step 1: Synthesis of Transparent Linear Polyamic Acid (A)>

In the first step, the transparent linear polyamic acid (A) ismanufactured from tetracarboxylic acid dianhydrides in (a-1) anddiamines in (a-2) in the usual method of manufacturing polyamic acid. Inother words, it is possible to obtain linear polyamic acid (A)quantitatively by adding tetracarboxylic acid dianhydride to diamineslowly, which is then reacted for 24 hours in a reactor, of whichtemperature can be controlled, while maintaining the temperature belowroom temperature.

The solvent used for polymerization is one or more kinds of solventsselected from the group consisting of meta-cresol,N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide(DMAc), γ-butyrolactone, 2-butoxyethanol, and 2-ethoxyethanol. In somecases, organic acid such as para-toluene sulfonic acid, hydroxybenzoicacid, crotonic acid, etc. or an organic amine derivative, maybe added upto 5 weight % as an imidization catalyst relative to the total amount ofthe above reaction mixture. Further, hydroquinone or similar compoundmay be used as a thermopolymerization inhibitor in the range of 30 to500 ppm relative to the weight of the polymer. Still further, adhesionmay be improved by adding a siloxane diamine derivative within a rangeof 0.5 to 50 weight % with respect to the total amount of diaminenecessary.

The average molecular weight (Mw) of the linear polyamic acid thusobtained is characterized by being in the range of 2,000 to 200,000. Ifthe molecular weight is less than 2,000, it is difficult to form filmsthereafter; if it is higher than 200,000, it may be difficult to handlethem due to excessively high viscosity, and the degree of planarizationof the films formed thereafter may be worsened. The linear polyamic acidthus obtained shows photosensitivity when coupled with an appropriatephoto-initiator without multi-functional monomer since it hasethylenically unsaturated bonds at polymer side chain. Also, it isadvantageous to obtain films having superior chemical resistance afterpostbaking of polyamic acid. However, the linear polyamic acid withoutsubsequent treatment has a problem of narrow development margin sinceits solubility in an alkali developer is very good. <Step 2:Esterification with Ethylenically Unsaturated Compound (B)>

In the second step, to control the solubility of the linear polyamicacid in the alkali developer and to endow additional reactive site, thealkali-soluble linear polyamic acid (A) is esterified with anethylenically unsaturated compound (B) having an epoxy group in the samemolecule. The compound (B) includes allyl glycidyl ether,glycidyl(meth)acrylate, 3,4-epoxycyclohexyl(meth)acrylate, glycidyl5-norbornene-2-carboxylate (a mixture of endo and exo), glycidyl5-norbornene-2-methyl-2-carboxylate (a mixture of endo and exo),1,2-epoxy-5-hexene, 1,2-epoxy-9-decene, etc., which may be used singlyor in combination with two or more kinds of compounds duringesterification. It is preferable to use 10 to 400% equivalent weight ofthe compound (B) with respect to that of the total carboxylic acid groupin the linear polyamic acid (A). If this range is deviated, there may beproblems such as difficulty in controlling the solubility to thedeveloper or reduced heat resistance of the films thus formed.

The acid value of the reactive transparent polyimide precursor thusobtained is about 30 to 200 mg KOH/g, and the average molecular weightis within a range of 2,000 to 200,000, and more preferably, within arange of 5,000 to 100,000.

The reactive transparent polyimide precursors obtained in the above asshown in Chemical Formula 1 has more ethylenically unsaturated bonds perstructural unit compared to those of the linear polyamic acid (A), andtherefore, it is possible to manufacture negative-type photosensitiveresin compositions with enough development margin without additionalmulti-functional monomers; to reduce the amount of photo-initiatornecessary; and to improve photosensitivity.

Hereinafter, a method of manufacturing negative-type photosensitivetransparent polyimide precursor resin compositions by using the reactivetransparent polyimide precursors obtained in the above is described.

In order to manufacture a negative-type photosensitive transparentpolyimide precursor resin composition with the alkali developability, anappropriate photo-initiator (C) should be used, and if necessary,photosensitizer (D), multi-functional monomer (E), additive (F), etc.may be used in combination with the above.

The above alkali-soluble reactive transparent polyimide precursor (shownin Chemical Formula 1) may be used singly or in combination with two ormore kinds. It is preferable to use the reactive transparent polyimideprecursor in an amount of 10% to 99% of the total solid portion of thephotosensitive transparent polyimide precursor resin compositions. If itis less than 10%, the adhesion of the films thus formed is decreased; ifit is greater than 99%, there may be a problem of low photosensitivity.

Examples of the photo-initiator (C) include benzophenone,4,4′-bis(N,N-diethylamino)benzophenone,4,4′-bis(N,N-dimethylamino)benzophenone, phenylbiphenyl ketone,1-hydroxy-1-benzoylcyclohexane, benzil, benzyldimethyl ketal,2-benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone,2-methyl-4′-(methylthio)-2-morpholinopropiophenone, thioxanthone,1-chloro-4-propoxythioxanthone, isopropyl thioxanthone, diethylthioxanthone, ethyl anthraquinone, 4-benzoyl-4′-methyldiphenyl sulfide,benzoyl butyl ether, 2-hydroxy-2-benzoyl propane,2-hydroxy-2-(4′-isopropyl)benzoyl propane,4-butylbenzoyltrichloromethane, 4-phenoxy benzoyldichloromethane,benzoyl formic acid methyl, 1,7-bis(9′-acrydinyl)heptane,9-n-butyl-3,6-bis(2′-morpholinoisobutyroyl)carbazole,2,4,6-trimethylbenzoyl diphenylphosphin oxide, etc.

It is preferable to use 0.1 to 90 weight % of photo-initiator relativeto the amount of a polymer, more preferably, within a range of 0.2 to 50weight %. If it deviates from this range, there may be problems like nophoto-polymerization or reduced developability, etc.

As a photosensitizer (D), a coumarine derivative such as 3,3′-carbonylbis(dimethylamino)coumarine, etc., an aromatic carbonyl compound such asfluorenone, etc., an amine derivative such as triethylamine, etc., amethylenethiazole derivative such as 1,2-dihydronaphtho[1,2,d]thiazole,etc. may be used.

A multi-functional monomer (E) may be one of compounds having one ormore ethylenically unsaturated groups that may be additionallypolymerized in a molecule and with a boiling point of 100° C. or higher.Examples include phenoxyethyl methacrylate,polyethyleneglycol(meth)acrylate, polypropyleneglycol(meth)acrylate,trimethylolethane tri(meth)acrylate, trimethylolpropanetri(meth)acrylate, neopentyl glycol(meth)acrylate, pentaerythritoltriacrylate, pentaerythritol tetraacrylate, dipentaerythritolpentacrylate, dipentaerythritol hexacrylate, etc.

Also, functional monomers include caprolactone-modified KAYARAD DPCA-20,KAYARAD DPCA-30, KAYARAD DPCA-60, KAYARAD DPCA-120, etc. in the form ofbeing introduced to dipentaerythritol; KAYARAD TC-110S introduced totetrahydrofurfuryl acrylate, KAYARAD HX-220, KAYARAD HK-620, etc.introduced to neopentyl glycol hydroxypivalate, etc.

Other functional monomers include epoxy acrylates, novolak-epoxyacrylates that are bisphenol A derivatives; U-324A, U15HA, U-4HA, etc.that are urethane-group multi-functional acrylates. Functional monomershaving ethylenically unsaturated double bonds may be used singly or incombination with two or more kinds of monomers.

If necessary, additives (F) that are generally used as coating agentscan be included. Examples of F are thermopolymerization inhibitors suchas hydroquinone, 4-methoxyphenol, quinone, pyrocatechol, t-butylcatechol, phenothiazine, etc.; plasticizers; silicone-type adhesionpromotors; fillers; surfactants; etc.

Described below is a method of pattern formation by using anegative-type photosensitive transparent polyimide precursor resincomposition of the present invention, and then forming a heat-resistanttransparent polyimide film:

<Step 1>

A photosensitive polyimide precursor resin composition is coated onsubstrates. For substrates, glass or transparent plastic can be used inview of the characteristics of liquid crystal display devices, but notlimited as long as they meet the object of displaying. As to the methodof coating the photosensitive resin composition of the present inventionon the surface of a substrate, various kinds of coating methods such asspraying, roll coating, slit nozzle coating, rotatory coating, extrusioncoating, bar coating, etc. and combination of two or more kinds of theabove methods can be adopted. The thickness of coated films variesaccording to the method of coating, concentration of solids in thecomposition, viscosity, etc., but is usually 0.5 to 100 μm after theyare dried.

<Step 2>

In order to form non-fluxionary film after coating, prebake process, inwhich the solvent is volatilized under vacuum, infrared and/or heat, isperformed. Conditions for heating vary according to the kind or mixingratio of each component, but usually in the range of 60 to 130° C. for 5to 500 seconds on a hot plate, or 60 to 140° C. for 20 to 1,000 secondsin an oven.

<Step 3>

Thereafter, thin film of photosensitive polyimide precursor resincomposition is exposed using a mask having a predefined pattern.Exposure can be done by far-UV light such as eximer laser, etc., UV,visible light, e-beam, x-ray, etc. In the present invention, it ispreferable to use g-line (having a wavelength of 436 nm), h-line (havinga wavelength of 405 nm), and i-line (having a wavelength of 365 nm) ofmercury lamp. Exposure can be carried out by contact, proximity, orprojection method.

<Step 4>

Whether to perform post-exposure bake (PEB) prior to alkali developmentis optional. PEB step may be introduced if necessary. PEB temperature isnormally lower than 150° C., and PEB time is about 0.1 to 10 minutes.

<Step 5>

In the development process, non-exposed part of the film is removed byalkali developer. For the developer, an aqueous alkali solution composedof mineral alkalis such as sodium hydroxide, potassium hydroxide, sodiumcarbonate, sodium silicate, sodium meta-silicate, ammonia, water, etc.;primary amines such as ethylamine, n-propylamine, etc.; secondary aminessuch as diethylamine, di-n-propylamine, etc.; tertiary amines such astriethylamine, methyldiethylamine, n-methylpyrrolidone, etc.; alcoholamines such as dimethylethylalcohol amine, triethylalcohol amine, etc.;quarternary ammonium salts such as tetramethyl ammonium hydroxide,tetraethyl ammonium hydroxide, choline, etc.; and amines such aspyrrole, piperidine, etc. may be used.

It is also possible to use an aqueous solution in which an appropriateamount of water-soluble organic solvent such as methyl alcohol, ethylalcohol, propyl alcohol, isopropyl alcohol, propylene glycol monomethylether, dipropylene glycol monomethyl ether, etc.; and surfactant; etc.is added. Development time is usually about 10 to 200 seconds. Dipping,spraying, puddle, etc. are applicable for the development method. Afterdevelopment, deionized (DI) water rinse is done for 20 to 200 seconds,and moisture on the substrate is removed by spin drying or blowingcompressed air or nitrogen to give a desired pattern on the substrate.

<Step 6>

After development, polyimide precursor films are converted intoheat-resistant polyimide films through postbake (also called hardbake)on a hot plate or in an oven. Baking is usually done at 150° C. to 300°C. for 1 to 120 minutes on a hot plate, or for 10 to 120 minutes at thesame temperature range in an oven. Completely cross-linked and hardenedpolyimide pattern is obtained after postbake.

It is seen that the thermal decomposition temperature of polyimide filmsthus formed is in the range of 300 to 500° C., and transmittance between400 to 700 nm is higher than 90%. It is also seen that the dielectricconstant measured at 1 kHz is within a range of 2.5 to 4.0.

Heat-resistant polyimide films formed from the negative-typephotosensitive polyimide resin compositions of the present invention areused for protection layers, insulation layers, etc. of liquid crystaldisplay devices.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will become apparent from thedescription, or may be learned by practice of the invention.

MODES FOR CARRYING OUT THE INVENTION

First, polyimide precursors used for preferred embodiments andcomparative examples are synthesized in the following syntheticexamples, and the linear polyamic acid used for the following syntheticexamples is synthesized according to a known method. This is alsodescribed in detail in Korean Patent Application No. 10-2002-074070which is invented by the present inventors. In other words, diamine isdissolved in solvent under nitrogen gas flow in a reactor to which amixer, temperature controller, nitrogen inlet, and cooler are attached,and mixed while slowly adding tetracarboxlic acid dianhydride, where thereaction temperature is maintained below room temperature. The yield ofthe polymerization reaction is quantitative when the compounds arereacted for 12˜24 hours.

SYNTHETIC EXAMPLE 1

A 100 g portion of the linear polyamic acid solution (20% solids, acidvalue of 220 mg KOH/g, Mw=18,000) synthesized by reacting1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA) and2-(methacryloyloxy)ethyl 3,5-diaminobenzoate (DA-HEMA) inN-methyl-2-pyrrolidine (NMP)/γ-butyrolactone (volume ratio=1/1)co-solvent is charged in a 250-ml round-bottom flask, stirred, andheated to 110° C. under nitrogen atmosphere.

Reactive polyimide precursor 1 is synthesized by adding 20 g of glycidylmethacrylate to the flask slowly in an hour, and allowing to react fortwo hours. The acid value of the reactive polyimide precursor thusobtained is 120 mg KOH/g.

SYNTHETIC EXAMPLE 2

Reactive polyimide precursor 2 is synthesized in the same method as thatin Synthetic Example 1 except that the linear polyamic acid (20% solids,acid value of 240 mg/g, Mw=22,000) is synthesized from 3,5-diaminophenylcinnamate instead of 2-(methacryloyloxy)ethyl 3,5-diaminobenzoate in theabove Synthetic Example 1. The acid value of the reactive polyimideprecursor thus obtained is 160 mg KOH/g.

SYNTHETIC EXAMPLE 3

Reactive polyimide precursor 3 is synthesized in the same method as thatin Synthetic Example 1 except that the linear polyamic acid (20% solids,acid value of 240 mg/g, Mw=22,000) is synthesized from coumaronyl3,5-diaminobenzoate instead of 2-(methacryloyloxy)ethyl3,5-diaminobenzoate in the above Synthetic Example 1. The acid value ofthe polyimide precursor thus obtained is 130 mg KOH/g.

SYNTHETIC EXAMPLE 4

Reactive polyimide precursor 4 is synthesized in the same method as thatin Synthetic Example 1 except that the linear polyamic acid (20% solids,acid value of 200 mg/g, Mw=26,000) is synthesized from 4,4-oxydianiline(ODA) instead of 2-(methacryloyloxy)ethyl 3,5-diaminobenzoate in theabove Synthetic Example 1. The acid value of the polyimide precursorthus obtained is 140 mg KOH/g.

SYNTHETIC EXAMPLE 5

Reactive polyimide precursor 5 is synthesized in the same method as thatin Synthetic Example 1 except that the linear polyamic acid (20% solids,acid value of 230 mg/g, Mw=28,000) is synthesized from pyromellitic aciddianhydride (PMDA) and 4,4-oxydianiline instead of1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA) and2-(methacryloyloxy)ethyl 3,5-diaminobenzoate in the above SyntheticExample 1. The acid value of the reactive polyimide precursor thusobtained is 140 mg KOH/g.

By using reactive polyimide precursors manufactured in the abovesynthetic examples, photosensitive resin compositions in the followingcomparative examples and preferred embodiments are manufactured:

[Preferred Embodiment 1]

Photosensitive polyimide precursor resin composition 1 is manufacturedby dissolving 0.5 g of CGI124 as a photo-polymerization initiator and0.01 g of BYK307 as a surfactant in 50 g of the reactive polyimideprecursor 1 solution manufactured in Synthetic Example 1 and filteringthe mixture with a 0.2μm filter. Films are formed by spin-coating theabove composition 1 on a glass substrate and pre-baking on a 100° C.-hotplate for 90 seconds. A photomask is put onto the films thus obtained,and 20 mW/cm² UV light is irradiated at 365 nm for 10 seconds by using amercury lamp. A pattern is formed by developing the films with 2.38weight % tetramethylammonium hydroxide aqueous solution at roomtemperature for 20 seconds, and washing it with DI water for 10 seconds.They are then hardened by postbake step in an oven at 250° C. for 1hour. The minimum line width of the films thus obtained is 25 μm (for1:1 line/space pattern), and the thickness is 1.2 μm.

[Preferred Embodiment 2]

The same processes as those in Preferred Embodiment 1 are performedexcept that the reactive polyimide precursor solution 2 manufactured inSynthetic Example 2 is used. The minimum line width of the films thusobtained is 25 μm, and the thickness is 1.2 μm.

[Preferred Embodiment 3]

The same processes as those in Preferred Embodiment 1 are performedexcept that the reactive polyimide precursor solution 3 manufactured inSynthetic Example 3 is used. The minimum line width of the films thusobtained is 30 μm, and the thickness is 1.2 μm.

COMPARATIVE EXAMPLE 1

The same processes as those in Preferred Embodiment 1 are performedexcept that the reactive polyimide precursor solution 4 manufactured inSynthetic Example 4 is used. The minimum line width of the films thusobtained is 50 μm, and the thickness is 1.2 μm.

COMPARATIVE EXAMPLE 2

The same processes as those in Preferred Embodiment 1 are performedexcept that the reactive polyimide precursor solution 5 manufactured inSynthetic Example 5 isused. The minimum line width of the films thusobtained is 50 μm, and the thickness is 1.2 μm.

COMPARATIVE EXAMPLE 3

The same processes as those in Preferred embodiment 1 are performed byusing the linear polyamic acid (20% solids, acid value of 220 mg KOH/g,Mw=18,000) which is not reacted with glycidyl methacrylate in SyntheticExample 1 instead of the reactive polyimide precursor solution 1, whereit is not possible to obtain a desired pattern having a appropriateshape, since the pattern is swept away in the process of development. Inorder to prevent pattern loss, post-exposure bake step at 160° C. for 10minutes should be added before development. Then, it is possible to forma desired pattern, where the minimum line width of the pattern thusobtained is 40 μm, and the thickness is 1.2 μm.

TESTING EXAMPLE

Physical properties of polyimide films obtained from the photosensitivepolyimide compositions in the above preferred embodiments are measuredin a method described below, and the results are shown in Table 1:

<Evaluation of Heat Resistance>

After the polyimide pattern is formed, the change in its thickness bythermal impact is monitored. It may be said that, the smaller the changein its thickness at high temperature, the better the heat resistance ofthe film is. The ratio of the post-baked film thickness to pre-bakedfilm thickness is defined as residual film ratio. If it is greater than95% after processing at 250° C. for 1 hour, it is defined to besuperior; if it is less than that, it is defined to be inferior.

<Evaluation of Transmittance>

After the polyimide pattern is formed, the transmittance between 400 nmto 700 nm is measured. If the transmittance is greater than 90%, it isdefined to be superior; if it is less than that, it is defined to beinferior.

<Evaluation of Chemical Resistance>

Chemical resistance is examined by observing the change in the thicknesswhen the films are dipped into chemicals (10% NaOH aqueous solution, 10%HCl aqueous solution, and NMP). ((Film thickness before treatment−Filmthickness after treatment)/(Film thickness before treatment))*100 (%) isdefined to be the ratio of change in thickness. The smaller the ratio ofchange in thickness when they are treated to chemical substances, thebetter the chemical resistance. When the ratio of change in thicknessafter dipping into chemical substances at room temperature for 1 hour iswithin ±3%, it is defined to be superior; when it exceeds that range, itis defined to be inferior.

<Evaluation of Planarization>

In order for films to be used for transparent protection layers forliquid crystal display devices, degree of planarization of the films ontopographical substrate is important. Degree of planarization is definedto be (1—(step height after coating)/(step height before coating))*100(%). For evaluation of the degree of planarization, 10 μm Line/10 μmSpace (1:1) repetitive pattern with 1.0 μm step height before coating isused. If degree of planarization is greater than 70%, it is defined tobe superior; if it is less than that, it is defined to be inferior.

TABLE 1 Film Minimum thickness Heat Chemical Degree of line Composition(μm) resistance Transmittance resistance planarization width Preferred1.2 μm Superior Superior Superior Superior 25 μm Embodiment 1 Preferred1.2 μm Superior Superior Superior Superior 25 μm Embodiment 2 Preferred1.2 μm Superior Superior Superior Superior 30 μm Embodiment 3Comparative 1.2 μm Superior Superior Inferior Inferior 50 μm Example 1Comparative 1.2 μm Superior Inferior Inferior Inferior 50 μm Example 2Comparative 1.2 μm Superior Superior Inferior Superior 40 μm Example 3

As seen in the above Table 1, in case of polyimide films of PreferredEmbodiments 1 to 3 of the present invention, it is seen that theirtransmittance, chemical resistance, and degree of planarization aresuperior compared to those of Comparative Examples 1 and 2. It is alsoseen that polyimide films show superior properties without additionalprocess compared to Comparative Example 3 which is a conventionalmethod.

INDUSTRIAL APPLICABILITY

As described in the above, the present invention can provide anegative-type photosensitive polyimide precursor composition havingsuperior heat resistance, transmittance, chemical resistance, and degreeof planarization, and thus is useful in that the above compositions maybe applicable for transparent protection layers or insulation layers ofliquid crystal display devices.

While the invention has been described in terms of a few preferredembodiments, those skilled in the art will recognize that the inventioncan be practiced with modification within the spirit and scope of theappended claims.

1. A reactive transparent polyimide precursor having the structure inthe following Chemical Formula 1:

where X is a tetra-valent organic group derived from alycyclictetracarboxylic acid dianhydrides having 3 to 30 carbon atoms; Y is adi-valent organic group derived from aliphatic, alicyclic, ornon-conjugated aromatic diamines which have 3-30 carbon atoms and sidechains, wherein the side chains have one or more ethylenicallyunsaturated bonds capable of being crosslinked by a radical; and R₁ andR₂ are, independent of each other, a hydrogen atom or an organic grouphaving 1 to 20 carbon atoms including one or more ethylenicallyunsaturated bond(s), provided that R₁ and R₂ are not hydrogen atoms atthe same time, wherein the acid value of said reactive transparentpolyimide precursor is within a range of 30 to 200 mg KOH/g, and saidreactive transparent polyimide precursor is a negative typephotosensitive precursor, wherein R₁ and R₂ including one or moreethylenically unsaturated bond(s) are derived from one or more compoundsselected from the group consisting of allyl glycidyl ether, glycidylacrylate, glycidyl methacrylate, 3,4-epoxycyclohexylmethyl acrylate,3,4-epoxycyclohexylmethyl methacrylate, glycidyl5-norbornene-2-carboxylate (a mixture of endo and exo forms), glycidyl5-norbornene-2-methyl-2-carboxylate (a mixture of endo and exo forms),1,2-epoxy-5-hexene, and 1,2-epoxy-9-decene.
 2. The reactive transparentpolyimide precursor according to claim 1, wherein the weight averagemolecular weight of said reactive transparent polyimide precursors iswithin a range of 2,000 to 200,000.